The essential functions and characteristics of a telecommunications system have been determined by a European standardization committee, the European Telecommunications Standards Institute, ETSI for short, in a European standard for cordless telecommunication, DECT in short, the Digital European Cordless Telecommunications--Standard. This DECT standard is the basis for a cordless private branch exchange to which base stations are connected through DECT interface circuits. Each base station supplies a radio cell in which it establishes the radio connection with the cordless telephones, see V. Werbus, A. Veloso, A. Villanueva: DECT: Mobility in wireless private branch exchanges of the new Alcatel generation. Electrical Communication, 2. quarter 1993, pages 172-180. The radio transmission takes place via ten carrier frequencies in a frequency band established by the DECT standard. As shown in FIG. 2 of the above-mentioned article, each of these carriers is subdivided into 24 time slots, where the first twelve are used for transmission from the base station to the cordless telephone, the remaining twelve for the inverse direction of transmission. In this way, twelve cordless telephones can be serviced simultaneously by one base station. Since the pulse code modulated (PCM)-coded speech is converted into Adaptive Differential Pulse Code Modulation (ADPCM)-code before the radio transmission, each base station must therefore contain an ADPCM/PCM transcoder for every potential call, as shown in FIG. 4 of the above-mentioned article. As also shown in FIG. 4 thereof, two base stations are managed by a special DECT interface circuit arrangement in the above named wireless private branch exchange (see FIG. 3 of the article). The two radio cells form a cell bundle. To reduce the expense of 24 ADPCM/PCM transcoders per cell bundle, 16 simultaneous communication connections per cell bundle are admitted according to the practical requirements, which are distributed to the two base stations according to need. Still, the cost of sixteen ADPCM/PCM transcoders is very high, and there is a desire to reduce the number of ADPCM/PCM transcoders without limiting the access possibilities, in order to attain a reduction in the costs. To always make the radio connection with the best quality available, and to enable the cordless telephone to make a change in location during a call, the DECT standard provides for an interruption-free channel change within a radio cell or a cell bundle. Although a change from one cell bundle to another is possible, it is only possible with an automatic reestablishment of a new connection. This involves a low data loss which does not disturb the voice transmission, but can lead to errors in the data transmission. It is therefore desirable to also be able to perform the change of a cell bundle, the so-called board-handover, without interruptions.